The present invention relates to illumination devices using a light-emitting diode and to display devices in which such illumination device is used as a backlight source for a non-luminous display panel.
With the recent improvement of the light emission efficiency of light-emitting diodes, light sources in various kinds of illumination devices have been changed from lamps or fluorescent lamps to light-emitting diodes. This is because the light-emitting diodes are meritorious in many points, that is, they are smaller in size, are capable of multi-colored light emission, are easily controllable, consume smaller electric power, and so forth. However, the light output and the efficiency of the light-emitting diode are not enough for illumination use in which a large light output is required or for display use in which an illumination device is used as a backlight source of a display panel. Thus, it is required to further increase the output light by improving the efficiency and to lower the power consumption.
As measures for enhancing the efficiency in the light extraction from a light-emitting diode without changing the structure of the light-emitting diode, it is known, for example, from JP-A-10-65220 that a light-emitting diode is sealed with a high refractive index resin and the resulting arrangement is further sealed at its periphery with a low refractive index resin.